Container refrigeration apparatuses including a refrigerant circuit performing a refrigerant cycle have been used to cool air in a container for use in, e.g., marine transportation (see, e.g., Patent Document 1). The container is loaded with plants such as bananas and avocados. Plants perform respiration by absorbing oxygen in the air and releasing carbon dioxide even after they have been harvested. The plants lose their nourishment and moisture as they respire. Thus, if the respiration rate of the plants increases, the degree of freshness of the plants decreases significantly.
Patent Document 1 discloses a container refrigeration apparatus including a gas supply device which supplies nitrogen-enriched air produced by separating nitrogen from air into a container. This container refrigeration apparatus supplies the nitrogen-enriched air into the container so that the air in the container has a lower oxygen concentration than the outside air, thereby reducing the respiration rate of the plants, and keeping the plants fresh easily.
To keep the plants fresh, a carbon dioxide concentration of the air in the container needs to be controlled appropriately in addition to the oxygen concentration. From this point of view, a container refrigeration apparatus which takes outside air into the container and exhausts inside air out of the container so that the composition of the air in the container (oxygen concentration and carbon dioxide concentration) is controlled to obtain a desired composition has been proposed. Another container refrigeration apparatus includes an intake passage through which a first space on the suction side of an interior fan communicates with the exterior of the container, and an exhaust passage through which a second space on the blowout side of the interior fan communicates with the exterior of the container, so that the air is taken in or exhausted by making use of a pressure difference produced between an inlet and an outlet of each passage while the interior fan is rotating.